The Biometry Core Unit is a centralized resource that provides direction and support for study design, data management, programming, computing, forms development, statistical analysis, psychometric testing, and training and supervision of interviewers. The Core serves investigators from the MAMDC, from Brigham and Women~s Hospital (particularly the Division of Rheumatology/Immunology and the Department of Orthopedics), from Harvard Medical School and Harvard School of Public Health. The Biometry staff and Executive Committee review and approve proposed projects. The Biometry Core staff advises on feasibility by examining sample size requirements, data sources, data management plans, data collection mechanisms, and analysis plans. This produces efficient studies likely to attain their goals. Thereafter, the Biometry Core collaborates throughout the project, refining analyses and monitoring the use of the data until the results are published. Some level of collaboration in all projects provides extra benefits; experience gained and techniques developed in one study carry over to subsequent studies, thereby achieving an economy of scale and stable research support by experienced specialists with diverse skills.